F Accessibility Support
Contents
This appendix is informative.
F.1 WAI Accessibility Guidelines accessibility guidelines
This appendix explains how accessibility guidelines published by
W3C's Web Accessibility Initiative (WAI) apply to SVG.
- The "Web Content Accessibility Guidelines 1.0" [ WCAG ] and "Web Content
Accessibility Guidelines 2.0" [ WCAG2 ] explain how authors can
create Web content that is accessible to people with
disabilities.
- The "Authoring Tool Accessibility Guidelines 1.0" [ ATAG ] explains how developers
can design accessible authoring tools such as SVG authoring tools.
To conform to the
SVG specification , an SVG authoring tool must conform to ATAG
(priority 1). SVG support for element grouping , reuse and navigation is relevant to
designing accessible SVG authoring tools.
- The "User Agent Accessibility Guidelines 1.0" [ UAAG ] explains how developers
can design accessible user agents such as SVG-enabled browsers.
To conform to the SVG
specification , an SVG user agent must conform to to the
Priority 1 accessibility guidelines defined in[ UAAG ] , and should conform also
to Priorities 2 and 3.UAAG. SVG support for scaling, the DOM, and
metadata are all relevant to designing accessible SVG user
agents.
The W3C Note "Accessibility Features of SVG" [ SVG-ACCESS ] explains in
detail how the requirements of the three guidelines apply to
SVG.
F.2 SVG Content Accessibility Guidelines content accessibility guidelines
This section explains briefly how authors can create accessible
SVG documents; it summarizes and builds upon "Accessibility
Features of SVG" [ SVG-ACCESS ].
- Provide text
equivalents for graphics.
-
- When the text content of a graphic (e.g., in a text
content element ) explains its function, no text
equivalent is required. Use the 'title' child element to explain the
function of text
content elements whose meaning is not clear from their
text content.
- When a graphic does not include explanatory text content, it
requires a text equivalent. If the equivalent is complex, use the
'desc' element, otherwise use the
'title' child element.
- If a graphic is built from meaningful parts, build the
description from meaningful parts.
- Do not rely on color alone.
-
- Do not use color alone to convey semantic information.
- Ensure adequate color contrast.
- Use markup correctly.
-
- Separate structure from presentation.
- Use the 'g' element and rich descriptions to
structure SVG documents. Reuse named objects.
- Publish highly-structured documents, not just graphical
representations. Documents that are rich in structure may be
rendered graphically, as speech, or as Braille. For example,
express mathematical relationships in MathML [ MATHML ] and use SVG for
explanatory graphics.
- Author documents that validate to the SVG RelaxNG grammar.
- Use text for text, and graphics for
graphics
-
- Represent text as character data, not as glyphs, images or
curves.
- Style text with fonts. Authors may describe their own fonts in
SVG.
- Do not use 'pi' fonts or picture fonts to represent small
graphics. The resulting garbage text does not conform to [ CHARMOD ] and confuses text to speech
engines.
- Provide a default reading order
-
- Use 'textArea' elements to
provide text that wraps in a box, rather than using script to wrap
the text or using a sequence of unrelated 'text' elements.
- Clarify natural language usage.
-
- Use
xml:lang 'xml:lang' to identify the natural
language of content and changes in natural language. This ensures
that textual content can be spell-checked, or converted to
speech.
- Use the 'systemLanguage'
test conditional processing
attribute to provide language-specific alternative text
and/or graphics.
- Allow for rich navigation
Do not assume that all devices have a pointer device.
Allow for keyboard navigation as well. Provide links for 8-way
directional navigation. Ensure that dynamic content is accessible.
Ensure that text equivalents for dynamic content are updated when
the dynamic content changes. Avoid storing dynamic text in
ecmascript arrays or in XSLT stylesheets. This makes it less
accessible